Anionic agent aftertreatment of cyanamide-modified cellulose



United States Patent 14 Claims. (Cl. 8116.2)

The present application is a continuation-in-part of application Serial No. 194,158 filed May 11, 1962, now abandoned, which is a division of application Serial. No. 821,675, filed June 22, 1959, now matured into US. Patent 3,051,698.

This invention relates to new substituted cellulose derivatives and to processes for making them.

The object of this invention is to provide new cationic, nitrogenated cellulose derivatives.

Another object is to provide new methods for making said cationic, nitrogenated cellulose derivatives.

Still another object is to provide cationic, nitrogenated cellulose derivatives which possess marked aflinity for acid or wool-types dyes as well as for other anionic conditioning or coating compositions, such as anionic resins and starches.

Other objects and advantages will become obvious from the following description.

We have discovered that when cellulose, both natural and regenerated, such as cellophane, viscose rayon and the like, and cellulose derivatives, such as cellulose esters of fatty acids, and cellulose xanthate, are treated with an aqueous alkaline solution of cyanamide, they react to form new cationic nitrogenated products. These nitrogenated products, when treated with an acid, form stable cationic acid salts. The aqueous alkaline cyanamide solution can be prepared by dissolving cyanamide in a solution of an alkali or alkaline earth metal base or by dissolving an alkali or alkaline earth metal cyanamide in water.

It will be understood that both in the specification and claims, the alkali metal and alkaline earth metal cyanamides include both the completely metallated cyanamide, such as CaNCN and Na NCN, and the metal hydrogen cyanamides, such as Ca(HNCN) or NaHNCN.

Conditions essential for the desired reaction include an aqueous solvent medium and an alkaline reaction mixture. For appreciable nitrogen add-on and cationicity, the pH should be above 7, preferably at least about pH 8.5 and preferably in the range of about 10 to 12.5.

Reaction of the cellulose or cellulose derivative with the cyanamide occurs at any temperature from the freezing to the boiling points of the reaction mixture. In general, reaction rate increases with increasing temperature. Thus for very rapid nitrogenation, the temperature can be elevated, as, for example, to about 200 F. However, digestion periods at such elevated temperatures are desir-ably shortened since, after a point of maximum substitution at the given reagent concentration, decomposition or rearrangement sets in, as demonstrated by some nitrogen loss.

Other conditions, such as the ratio of the cyanamide to the cellulosic material, the concentration of cyanamide dissolved in the reaction mixture, and the period of reaction, are not critical, although they do influence the extent of nitrogen substitution. For example, higher ratios of total cyanamide to the cellulosic material tend to increase the degree of substitution.

The precise nature of the reaction mechanism or of ice the substituent nitrogen-containing radicals is not yet completely understood. It is likely that reactive hydroxyl groups of the cellulose or cellulose ester participate in the reaction. In the case of cellulose esters, such as cellulose acetate, such free hydroxyl groups can be initially present or can be produced by hydrolysis under the alkaline conditions of the reaction. When .an alkali metal or alkaline earth metal cyanamide is dissolved in Water or when cyanamide is dissolved in an aqueous alkaline solution, the (HNCN) ion is formed. We consider it probable that this ion is the reactive agent. It will be understood, however, that the invention is not to be restricted by the foregoing hypothesis.

As aforementioned, the aqueous cyanamide treatment is effective with cellulose in its natural or regenerated forms, with fatty acid esters of cellulose, such as cellulose acetate, cellulose propionate, celluose butyrate and mixed esters, such as cellulose acetate propionate and cellulose acetate butyrate, and with cellulose xanthate. The cellulosic material can be treated in any desired physical form, as, for example, in the form of a fiber, pulp, or granule slurry, woven cloth, paper sheets, or plastic films. The cellulose can be derived from any source such as wood, cotton, straw, pith, and the like. Cellulose xanthate can be treated in solution.

The nitrogen-containing reagent, as previously stated, is cyanamide dissolved in an aqueous alkaline solution, preferably of an alkali metal or alkaline earth metal base, such as sodium, potassium, lithium, calcium, barium or strontium hydroxide, or their basic salts, or an aqueous solution of an alkali metal or alkaline earth metal cyanamide, such as sodium, potassium or calcium cyanamide. It is ordinarily not necessary to add a base to a solution of the cyanamide salt since solutions of such salts in Water are generally sufiiciently alkaline. An aqueous solution of calcium cyanamide, for example, generally has a pH in the range of about 10.5 to 11.9. An alkali metal or alkaline earth metal cyanamide hydrolyzes in water to form a solution which is substantially similar to an aqueous solution of cyanamide in an alkaline solution of an alkali metal or alkaline earth metal base. In general, we prefer to employ calcium cyanamide because of its availability, low cost, and high efficiency.

The reaction mixture containing the cellulosic material is maintained at the desired reaction temperature for a sufiicient length of time to obtain the desired degree of nitrogen substitution. Reaction occurs at a substantial rate at reduced to ordinary temperatures. This is an advantage where elevated temperatures .are either unfeasible or undesirable. For more rapid reaction rates, the reaction temperature can be increased. There is ordinarily no economic advantage in continuing the reaction period beyond the point at which the desired or maximum degree of substitution is achieved. In some cases, particularly at elevated temperatures, there may be some loss of substituted nitrogen with prolonged treatment, although a cationic, nitrogenated product is still obtained.

The cationic, nitrogenated cellulosic products can be separated from the alkaline reaction mixture, washed, dried, and employed as such. They can also be acidified to form the cationic acid salts, which, in many cases, are preferred as, for example, Where the cellulosic product is to be dyed with an acid dye salt.

The acid salt derivatives can be prepared from the washed and dried nitrogenated products by treating them with an aqueous solution of the desired acid. Ordinarily, they are 'most conveniently prepared by acidification of the alkaline reaction mixture with the particular acid, the derivative of which is desired. The pH is preferably reduced to 4 or less, in some cases, to as low as 1. Where operational expediency requires that the cyanamide reaction period be short, it may be desirable to dry the treated cellulosic derivative, without washing prior to acidification since this increases the nitrogen add-on.

Substantially any acid can be used, including inorganic and organic acids, such as hydrochloric, nitric, sulphuric, 5

sulfurous, phosphoric, acetic, propionic acids, and the like. In general, we prefer to employ hydrochloric acid.

The acidification treatment can be carried out at reduced, ambient or elevated temperature, as, for example,

the temperature of the initial nitrogenation reaction. After the acid treatment is completed, the nitrogenated cellulose product acid salts can be removed from the reaction mixture, washed, and dried in any convenient manner.

The cationic, nitrogenated, cellulose derivatives possess the dyeing properties of Wool and can readily be dyed with acid dyestuffs such as light green SF yellowish (Cl. 670, Merck Index, 6th edition, page 573), acid fuchsine (Cl. 692, trisodium salt of the trisulfonic acid of parafuchsine), cosine Y (Cl. 768, disodium salt of 2,4,5,7-

tetrabrorno 9 O carboxyphenyl-6-hydroXy-3-isoxanthone), orange G (CL 27, disodium salt of l-phenylazo- Z-naphthol of 6,8-disulfonic acid), and the like.

The cationic cellulose derivatives are also substantive to anionic treating and coating compositions, such as anionic emulsions of urea-formaldehyde, melamine-formaldehyde, polystyrene, acrylic resins, vinyl resins, rubber,

rosin, and the like. Starch sizing is also improved.

Paper furnish such as sulfate, soda, sulfite or groundwood pulp, can be treated with cyan-amide directly in the beater and, thereby, provides a highly advantageous means for improving the retention of rosin and starch size and other polymeric compositions added to impart such properties as wet strength and water resistance to the paper.

Cotton and viscose nayons can be treated in form of fiber, yarn or cloth by immersion in the cyanamide reaction solution. Regenerated cellulose in sheet or film form, such as cellophane, can similarly be modified. The cellulose esters, such as cellulose acetate, can be treated in granule, fiber, yarn, woven cloth or film form.

EXAMPLE 1 Part I 90 grams of calcium cyanamide were slurried in 300 mls. of water for 15 minutes at 78 F. The solution was filtered, the filter cake washed with 200 mls. of water, and the washings added to the filtrate. The filtrate was acidified with cool 20% sulfuric acid to a pH of 5.0. The precipitated calcium sulfate was filtered off and washed with 50 mls. of water, the washings being added to the solution of cyanamide. The cyanamide solution was divided into 4 equal portions labelled A, B, C and D, into each of which was introduced 18 grams of sliver cotton (Scientific Products 61453A). The pH of each test mixture was adjusted as follows:

A to pH 11.6 with NaOH A B C D Untreated Cotton pH reaction slurry after 24 hours. 11.7 9.8 5.3 3. 5 Na Percent dry basis 0.167 0.071 0. 038 0.038 0. 030 Dyeresults None None None 1 Bright Green. 2 Light Green.

It will be noted that nitrogen add-on when the cyanamide digestion was carried out at acid pH was negligible and there was no appreciable substantivity to an acid dye.

Part II Reaction mixtures prepared similar to A above were digested at 32 F. for the indicated time intervals.

Hrs: Percent N DE. 24 0.093 48 0.124 72 0.171

All 3 of these samples dyed well with Cl. 670, the color becoming progressively deeper as the percent of nitrogen add-on increased.

EXAMPLE 2 Part1 Control A B C Percent N D.B 0.02 0.09 0. 10 0. l2 Dye results None 1 Light Green. 2 Deep Green.

This data demonstrates the improved take up of an acid dye salt by the cationic HCl salt of the nitrogenated cellulose fabric C as compared with that of the cationic nitrogenated parent derivatives, A and B.

PartII 100 tmls. of 0.5 molar Ca(HNCN) pH 11.8, were poured into each of 7 beakers and the pH adjusted as shown below. One each of 7 muslin strips was wetted and squeezed in each of the solutions, and placed in a covered beaker for 4 hrs. at 78 F. 100 mls. of water were added to each beaker and adjusted to pH 3.7. The strips were then washed, dried, and a portion of each dyed with a B to pH 9.6 with NaOH 0.01 solution of Cl. 670, washed and dried.

H 11.8 l ercent N 2, DB 0.20 1 5 3: 82 6. 0 5' 0 3 7 2' o Dye None None None None None Deep Green. 2 Medium Green.

C as is pH 5.0 Part III D to pH 3.6 with HCl All samples were maintained at 78 F. for 24 hours,

Strips of muslin were treated with solutions of Ca(HNCN) at pH 11.8 at the temperatures and for the time intervals set out below, with the pH subsequently adjusted to 3.7 w1th HCl, using the procedure described in Part II, and

dyed with 0.01% solutions of Cl. 670.

Substantial reaction in this case occurred only at a pH 78, 78, 70, 200, 32.5", above 10. A dyed a deep green with Cl. 670, B dyed 5 min. 1 hr. 24 hrs. 1 hr. 24 hrs. Slightly and the others not at all. P t N D.B 0. 026 0. 041 0.210 0.10 0. 05 v $5521- None a Part II 5 Runs similar to I-A were repeated except that diges- Light Green. Deep Green. trons were earned out at the temperatures and t1me pe- 3 Medium Green. riods set out below.

200 F. 325 F. 51 1iin. 1 l 1 r. l1 rs. 24% rs. 48 l 1 rs. 72 1's.

Percent N2,D.B 0.154 0.105 0.039 0.073 0.077 0.080

EXAMPLE 3 20 (l) and (5) dyed a medium light green. (2), (4) and 100 guns. of desized muslin fabric were immersed in (6) dyed lightly (3) did not 400 mls. of an aqueous extract containing 0.525 moles of EXAMPLE 5 calcium cyanamide for 16 hours. at 78 F. The pH was adjusted to 2.0 with HCl and the fabric Washed, dried and 2f rt I dyed with Cl. 670. The percent N of the untreated con- 0 trol was 0. 02% and that of the cyanamide treated sample I a re 1 0.45% The control did not dye whereas the treated fabric g fgf i j sigiig i g 5 2:2 g fi gfg g g tiig dyed a deep, Inform greendigested with 18% NaOH at 73 F. for 1 hr. The caustic EXAMPLE 4 was poured off and the pulp pressed to a Weight of 300 gms. It was then shredded and aged for 65 hrs. in sealed Part I jars at 73 F. The treated pulp was divided into 5 por- 90 gms. of sulfite pulp were slurried in 500 mls. of tions; pH was adjusted with HCl; and calcium cyanamide water which was divided into 5 equal parts. pH of the solution added.

The procedure was similar to that of Example 4, Part Pulp A B o D 1011 after 24 hrs 11. 7 10. 9 7. 2 3. 0 2.1 PercentNz, D.B 0.000 0.145 0.140 0. 054 0.002 0.001

slurry was 5.2. 90 gms. of hydrated grade calcium cyan- A and B dyed a medium light green, the others not at amide were slurried in 300 mls. of water for 15 min. at all. 78 F. and filtered. The filter cake was washed with 200 P t II mls. of water and the washings added to the filtrate. The

calcium cyanamide extract was divided into 5 equal por- Runs similar to LA were made at difierent temperations labelled A, B, C, D and E. A was added to one of tures and for different time intervals.

5 min. 1 hr. 20 hrs. 24 hrs. 48 hrs. 72 hrs. Percent N2, D .B 0. 220 0. 158 0.027 0.144 0. 249 0.158

the sulfite pulp portions Without adjustment of the 11.3 pH. The pH of B, C, D and E was adjusted with HCl to 9.6, 7.0, 3.7 and 2.0 respectively and the sulfite portions added. After 24 hrs. at 78 F., all samples were taken to (1), (4), (5) and (6) dyed deep green. (2) dyed a pH 2.0 with HCI, filtered, Washed and dried. medium green. (3) did not dye.

Sulfite Pulp A B C D E DH after 24 hrs 11. 9 10. 4 9. 2 4. 7 2. 6 Percent N2, D.B 0. 00 0. 26 0. 14 0. 03 0. 02 0. 01

EXAMPLE 6 treatment at the temperatures and for the times indicated,

the pH was reduced to 2.0 with HCl. The treated cellu- The following pulps were Obtained from the beater of lose acetate was then filtered, washed and dried.

a paper mill and partially dewatered.

1 Medium Green.

The acetyl content of a sample treated at 32.5 F. for Oak Chip Kraft Straw Waste 72 hours, nitrogen add-on 0.177%, was 29.00%, indi- Paper eating a substantial degree of hydrolysis.

2 1g solids, perDcefitnn t, nitrogfiifi pmm EXAMPLE 9 DB 0.097 0.000 0.211 0.051 C0101 Whlte (2) (2) A similar procedure was employed as in Example 9, rm Brown, except that the cellulose acetate powder used was Du- Dark BIOWH- Pont Z-a 558--p, percent acetyl 40.42, D.S. 2.52.

78 F. 200 F. 325 F. Blank 24 hrs.

5min. 1hr. 24 hrs. 48hrs.

Percent N2,D.B 0.000 0. 050 0. 008 0.076 0.071 0.085 Dye None V 1 Deep Green.

18 gms. D.B. (dry basis) of each of the pulps were The acetyl content of a sample treated at 325 F. for

diluted with 1000 mls. of water. 12 gms. CaNCN were 72 hours, nitrogen addon 0.09%, was 29.80%, indicating added to the straw pulp and the waste paper pulp. The asubstantial degree of hydrolysis. extract obtained by digesting 12 gms. CaNCN in 200 Regenerated cellulose can be cationical-ly nitrogenated mls. of water plus 125 mls. of water used to wash the with the cyanamide very conveniently during an interfilter cake was employed with the oak chip pulp and the mediate stage in processing, by addition of the cyanamide kr ft ul to the xanthate. Upon acidification, the xanthate decom- Produet Oak Chip Kraft Straw Waste Temperature, F 78 78 200 78 78 78 True (111111.) 5 24 5 4s 5 5 Percent N2, D.B 0.227 0. 27s 0. 097 0. 149 o. 240 0. 144

Dye 0.1. 670 t) Hours.

2 Medium Green. 3 Light Green. 4 Deep Green.

EXAMPLE 7 poses to form a cationic acid salt of a nitrogenated cellulose. The cellulose nitrate coating was peeled from a sheet of cellophane by immersing in water for 10 min. at 120 EXAMPLE 10 F. 10 gms. of the viscose sheet were immersed in 460 E mls. of a solution containing 0.704 moles of calcium cyan- 100 gm. of sulfite pulp were mixed with 18% NaOH amide. After 16 hrs. at 78 F. the pH was adjusted to and allowed to stand for 1 hr. at 73 F. The caustic was 2.0 with HCl. The treated film was washed and a portion then poured off and the pulp pressed to a weight of 300 y y immersion in 001% h film dye a gms. The press cake was shredded and allowed to age deep, clear green. A portion of the untreated sheet did fo 65 hrs, in a sealed jar at 73 F. 32 gms. CS were not dye at all. added to form the xanthate and the mixture shaken EXAMPLE 8 for hrs. at 78 F. The material was divided into 2 equal portions. p 18 gms. of cellulose acetate powder (DuPont WA 526- 13% N and 382 mls. Water were added X-P, percent acetyl 38.49, D.S. 2.32) slurried in 100 to POIUOHAafld Sflffed Zh mls. of water were added to 100 mls. of a solution of 25 g CN W re sl rried in 500 mls. water for calcium cyanamide prepared by extracting 90 gms. with 30 min. at 78 F. 21 gms. Na CO were added. The mix- 500 mls. of water. pH of the mixtures was 10.4. Afier ture was stirred for 5 min. and filtered. The filtrate, 470

9 mls., was added to portion B and the mixture stirred for 2 hrs. A and B were stored at 73 F. for 16 hrs.

200 mls. of A and B were each poured into 200 rnls. of water containing 50 mls. glacial acetic acid. The nitrogenated, regenerated cellulose acid salt was filtered, washed and air dried.

1 Deep Green.

Although this invention has been described with reference to illustrative embodiments thereof, it will be apparent to those skilled in the art that the principles of this invention can be embodied in other forms but within the scope of the claims.

The invention is hereby claimed as follows:

1. A process for adhering an anionic material to a cellulosic material selected from the group consisting of cellulose, fatty acid esters of cellulose and cellulose Xanthate which consists essentially of treating said cellulosic material with an aqueous alkaline solu tion of a substance from the group consisting of cyanamide, alkali metal and alkaline earth metal salts of cyanamide until a cationic nitrogenated material is obtained having an added nitrogen content of at least 0.041% by weight calculated on the dry weight of the cellulosic material, and then bringing said cationic nitrogenated material into contact with an anionic material to be adhered thereto from the group consisting of anionic resins and starches.

2. A process as claimed in claim 1 in which said anionic material is an anionic resin.

3. A process as claimed in claim 1 in which said anionic material is a starch.

4. A process as claimed in claim 1 in which said cationic nitrogenated material is dried before bringing it into contact with said anionic material.

5. A process as claimed in claim 1 in which said anionic material is in the form of an aqueous dispersion.

6. A process as claimed in claim 1 in which the pH during the treatment with the alkaline solution is between 8.5 and 12.5.

7. A process as claimed in claim 1 in which the temperature of the treatment with said alkaline solution is within the range of 32 F. to 200 F.

3. A process as claimed in claim 1 in which the cellulosic material is a paper pulp.

9. A process for adhering an anionic material to cellulose which consists essentially of treating the cellulose with an aqueous alkaline solution of a substance from the group consisting of cyanamide, alkali metal and alkaline earth metal salts of cyanamide until a cationic nitrogenated material is obtained containing at least 0.041% by weight of added nitrogen, calculated on the dry weight of the cellulose, reducing the pH of the solution to the acid side, and thereafter bringing the resultant cationic nitrogenated material into contact with an anionic material to be adhered thereto from the group consisting of anionic resins and starches.

10. A process as claimed in claim 9 in which the pH on the acid side is around 1 to 4.

11. A process for adhering an anionic material in dispersed form to cellulose which consists essentially of treating cellulose with an aqueous alkaline solution of a substance from the group consisting of cyanamide, alkalirnetal and alkaline earth metal salts of cyanamide until a cationic nitrogenated cellulose is obtained containing at least 0.041% by weight added nitrogen, calculated on the dry Weight of the cellulose, acidifying said solution to lower the pH to the acid side, thereafter drying the resultant cationic nitrogenated cellulose, and thereafter bring ing said cationic nitrogenated cellulose into contact with a dispersed anionic material to be adhered thereto from the group consisting of anionic resins and starches.

12. A process as claimed in claim 11 in which said cationic nitrogenated cellulose is dried before being acidified.

13. A process for adhering a dispersed anionic material to a cellulosic material from the group consisting of cellulose, fatty acid esters of cellulose and cellulose xanthate which consists essentially of reacting said cellulosic material with an aqueous alkaline solution of a substance from the group consisting of cyanamide, alkali metal and alkaline earth metal salts of cyanamide at a pH within the range of 8.5 to 12.5 at a temperature with the range of 32 F. to 200 F., until a cationic nitrogenated material is obtained containing at least 0.041% by weight added nitrogen, calculated on the dry weight of the material, bringing the resultant cationic nitrogenated material into contact with an acidic aqueous solution at a pH within the range of 1 to 4 and a temperature within the range of 32 F. to 200 F., washin and drying the resultant acidified material, and thereafter bringing the material thus obtained into contact with a dispersion of an anionic material to be adhered thereto from the group consisting of anionic resins and starches.

14. A process as claimed in claim 13 in which the cellulosic material is cellulose.

References Cited UNITED STATES PATENTS 2,234,889 3/1941 Boulton 8--54.2 X 2,318,464 5/1943 Cameron et al 8-54.2 X 2,530,261 11/1950 Morton et al. 8-1162 2,538,903 1/1951 Gaver et al. 260224 X 3,051,691 8/1962 Elizer et a1. 26091.3 3,051,698 8/1962 Elizer et al. 260212 3,051,699 8/1962 Elizer et a1 260233.3

NORMAN G. TORCl-HN, Primary Examiner. I. TRAVIS BROWN, Examiner.

I. CANNGN, Assistant Examiner. 

1. A PROCESS FOR ADHERING AN ANIONIC MATERIAL TO A CELLULOSIC MATERIAL SELECTED FROM THE GROUP CONSISTING OF CELLULOSE, FATTY ACID ESTERS OF CELLULOSE AND CELLULOSE XANTHATE WHICH CONSISTS ESSENTIALLY OF TREATING SAID CELLULOSIC MATERIAL WITH AN AQUEOUS ALKALINE SOLUTION OF A SUBSTANCE FROM THE GROUP CONSISTING OF CYANAMIDE, ALKALI METAL AND ALKALINE EARTH METAL SALTS OF CYANAMIDE UNTIL A CATIONIC NITROGENATED MATERIAL IS OBTAINED HAVING AN ADDED NITROGEN CONTENT OF AT LEAST 0.041% BY WEIGHT CALCULATED ON THE DRY WEIGHT OF THE CELLULOSIC MATERIAL, AND THEN BRINGING SAID CATIONIC NITROGENATED MATERIAL INTO CONTACT WITH AN ANIONIC MATERIAL TO BE ADHERED THERETO FROM THE GROUP CONSISTING OF ANIONIC RESINS AND STARCHES. 